1 (define (test-case actual expected)
2   (newline)
3   (display "Actual:   ")
4   (display actual)
5   (newline)
6   (display "Expected: ")
7   (display expected)
8   (newline))
9 
10 ;; Exercise 2.39.   Complete the following definitions of reverse (exercise 2.18) in terms of fold-right and fold-left from exercise 2.38:
11 
12 (define (reverse-right sequence)
13   (fold-right (lambda (x y) 
14 		(append y
15 			(list x)))
16 	      '()
17 	      sequence))
18 (define (reverse-left sequence)
19   (fold-left (lambda (x y) 
20 	       (cons y x))
21 	     '()
22 	     sequence))
23 
24 ;; '(1 2 3 4 5 6)
25 ;; (iter (op result (car items)) (cdr items))
26 (test-case (reverse-right '(1 2 3 4 5 6)) '(6 5 4 3 2 1))
27 (test-case (reverse-right '((1 2) (3) (4 (5 6)))) '((4 (5 6)) (3) (1 2)))
28 (test-case (reverse-left '(1 2 3 4 5 6)) '(6 5 4 3 2 1))
29 (test-case (reverse-left '((1 2) (3) (4 (5 6)))) '((4 (5 6)) (3) (1 2)))